CN218243836U

CN218243836U - MEMS structure

Info

Publication number: CN218243836U
Application number: CN202221644135.8U
Authority: CN
Inventors: 李冠华; 刘端
Original assignee: Anhui Aofei Acoustics Technology Co ltd
Current assignee: Anhui Aofei Acoustics Technology Co ltd
Priority date: 2022-06-27
Filing date: 2022-06-27
Publication date: 2023-01-06
Anticipated expiration: 2032-06-27

Abstract

The application discloses MEMS structure includes: a substrate having a ring body, a support beam and a support post formed in the ring body; a support table formed above the support columns; a piezoelectric composite vibration layer formed above the support stage and having an edge isolated from the substrate by a gap. Because the center of the piezoelectric composite vibration layer is fixedly supported and the edge of the piezoelectric composite vibration layer is suspended, the piezoelectric composite vibration layer can freely stretch and deform in the surface to release residual stress.

Description

MEMS structure

Technical Field

The present application relates to the field of MEMS (Micro-Electro-Mechanical systems, i.e. Micro-Electro-Mechanical systems), and more particularly, to a MEMS structure.

Background

MEMS microphones (microphones) mainly include both capacitive type and piezoelectric type. The MEMS piezoelectric microphone is a microphone prepared by utilizing a micro-electro-mechanical system technology and a piezoelectric film technology, and has small size, small volume and good consistency because of adopting the technologies such as a semiconductor plane process, bulk silicon processing and the like. Meanwhile, compared with a capacitor microphone, the MEMS piezoelectric microphone also has the advantages of no need of bias voltage, large working temperature range, dust prevention, water prevention and the like, but larger residual stress can be generated in the production and manufacturing process of the MEMS piezoelectric microphone, so that the development of the MEMS piezoelectric microphone is restricted. Due to the existence of residual stress, the device sensitivity is low, the stability is poor and the like.

SUMMERY OF THE UTILITY MODEL

To address the problems in the related art, the present application provides a MEMS structure capable of reducing residual stress.

The technical scheme of the application is realized as follows:

according to an aspect of the present application, there is provided a MEMS structure comprising:

a substrate having a ring body, a support beam and a support pillar formed in the ring body;

a support table formed above the support columns;

a piezoelectric composite vibration layer formed above the support stage and having an edge isolated from the substrate by a gap.

The substrate further comprises a cavity formed in the ring body, the supporting columns are fixed to the ring body through the supporting beams, and the cavity penetrates through the substrate.

Wherein the support post is formed at a center of the ring body.

Wherein the piezoelectric composite vibration layer includes:

a vibration layer formed above the support table, and an edge of the vibration layer is isolated from the substrate through the gap;

a first electrode layer formed over the vibration layer;

a piezoelectric layer formed over the first electrode layer;

a second electrode layer formed over the piezoelectric layer, wherein the second electrode layer comprises spaced apart inner and outer layers.

Wherein the area of the vibration layer is larger than the area of the cavity, and the area of the vibration layer is partially overlapped with the area of the ring body.

Wherein the inner layer has an inner diameter equal to the outer diameter of the support table and the outer layer is separated from the inner layer by a groove.

In summary, in the MEMS structure provided, the piezoelectric composite vibration layer is supported at the center and suspended at the edge, so that the piezoelectric composite vibration layer can freely stretch and deform in the plane to release the residual stress.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

FIG. 1 illustrates a perspective view of a MEMS structure provided in accordance with some embodiments;

FIG. 2 illustrates an exploded view of a MEMS structure provided in accordance with some embodiments;

FIG. 3 illustrates a bottom view of a substrate provided in accordance with some embodiments;

FIG. 4 illustrates a cross-sectional view of a MEMS structure provided in accordance with some embodiments.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments that can be derived from the embodiments given herein by a person of ordinary skill in the art are intended to be within the scope of the present disclosure.

Referring to fig. 1, in accordance with an embodiment of the present application, a MEMS structure is provided that may be used in, but is not limited to, a sensor such as a microphone or microphone, or other actuator. The MEMS structure includes a substrate 10, a support stage 14 (shown in fig. 2), and a piezoelectric composite vibration layer 20. The structure of the MEMS will be described in detail below.

Referring to fig. 2 and 3, the substrate 10 has a ring body 11, support beams 12 and support columns 16 formed in the ring body 11, and a cavity 13 formed in the ring body 11. The support posts 16 are fixed to the ring body 11 by support beams 12, and the cavities 13 penetrate the substrate 10. A support post 16 is formed at the center of the ring body 11. The substrate 10 comprises silicon or any suitable silicon-based compound or derivative (e.g., silicon wafer, SOI, polysilicon on SiO 2/Si). In some embodiments, there are two interdigitated support beams 12 within the loop 11. Support columns 16 are formed at the intersections of the support beams 12.

Referring to fig. 2 and 4, wherein fig. 4 is a sectional view taken along line a of fig. 3. The support table 14 is formed above the support column 16. In some embodiments, the support table 14 is shaped similarly to the support column 16.

The piezoelectric composite vibration layer 20 is formed over the mount 14 and the edge of the piezoelectric composite vibration layer 20 is isolated from the substrate 10 by a gap 15. Because the center of the piezoelectric composite vibration layer 20 is fixedly supported and the edge is suspended, the piezoelectric composite vibration layer 20 can freely stretch and deform in the plane to release the residual stress. Moreover, by adjusting the size of the gap 15 between the piezoelectric composite vibration layer 20 and the edge of the substrate 10, the sound leakage phenomenon of the MEMS structure can be effectively suppressed.

Referring to fig. 2, the piezoelectric composite vibration layer 20 includes a vibration layer 20e, a first electrode layer 20d, a piezoelectric layer 20c, and a second electrode layer, which are sequentially stacked from bottom to top. A vibration layer 20e is formed over the support stage 14, and the edge of the vibration layer 20e is isolated from the substrate 10 by a gap 15. Wherein the second electrode layer comprises an inner layer 20a and an outer layer 20b spaced apart. The piezoelectric layer 20c can convert the applied pressure into a voltage, and the first electrode layer 20d and the second electrode layer can transmit the generated voltage to other integrated circuit devices.

The area of the vibration layer 20e is larger than that of the cavity 13, and the area of the vibration layer 20e partially overlaps with that of the ring body 11.

The inner layer 20a has an inner diameter equal to the outer diameter of the support table 14 and the outer layer 20b is separated from the inner layer 20a by a groove. Wherein the first electrode layer 20d is grounded. Only the inner layer 20a of the second electrode layer is active and the outer layer 20b of the second electrode layer is inactive. This arrangement of the second electrode layer can effectively improve the sensitivity and reduce the influence of stray capacitance.

In some embodiments, the vibration layer 20e includes a single or multi-layer composite membrane structure of silicon nitride (Si 3N 4), silicon oxide, single crystal silicon, polycrystalline silicon, or other suitable support material. In some embodiments, the piezoelectric layer 20c includes zinc oxide, aluminum nitride, an organic piezoelectric film, lead zirconate titanate (PZT), a perovskite-type piezoelectric film, or other suitable materials. The first electrode layer 20d and the second electrode layer include aluminum, gold, platinum, molybdenum, titanium, chromium, and composite films composed thereof or other suitable materials.

In summary, in the MEMS structure provided, firstly, the center of the piezoelectric composite vibration layer 20 is fixed and the edge is suspended, so that the piezoelectric composite vibration layer 20 can freely stretch and deform in the plane to release the residual stress. Secondly, the first electrode layer 20d is grounded, only the inner layer 20a of the second electrode layer works, and the outer layer 20b of the second electrode layer does not work, so that the second electrode layer can effectively improve the sensitivity and reduce the influence of stray capacitance. Finally, by adjusting the size of the gap 15 between the piezoelectric composite vibration layer 20 and the edge of the substrate 10, the sound leakage phenomenon of the MEMS structure can be effectively suppressed.

The present invention is not intended to be limited to the particular embodiments shown and described, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A MEMS structure, comprising:

a support table formed above the support columns;

2. The MEMS structure of claim 1, wherein the substrate further comprises a cavity formed in the ring, the support posts being secured to the ring by the support beams, the cavity penetrating the substrate.

3. The MEMS structure of claim 2, wherein the support posts are formed at a center of the ring body.

4. The MEMS structure of claim 2, wherein the piezoelectric composite vibration layer comprises:

a first electrode layer formed over the vibration layer;

a piezoelectric layer formed over the first electrode layer;

a second electrode layer formed over the piezoelectric layer, wherein the second electrode layer includes an inner layer and an outer layer that are spaced apart.

5. The MEMS structure of claim 4, wherein the area of the vibration layer is larger than the area of the cavity, and the area of the vibration layer partially overlaps the area of the ring.

6. The MEMS structure of claim 4, wherein the inner layer has an inner diameter equal to an outer diameter of the support table, and the outer layer is separated from the inner layer by a trench.